Method and apparatus for testing floor coverings



June 6, 1967 Y 3,323,349

METHOD AND APPARATUS FOR TESTING moon COVERINGS P. R. SAVAGE ETAL FiledSept. 21, 1964 INVENTORS PRESTON R. SAVAGE GENE A. BROOKS ATTORNEZ Ml M&

W Pew United States Patent 3,323,349 METHOD AND APPARATUS FOR TESTINGFLOOR COVERINGS Preston R. Savage and Gene A. Brooks, Decatur, Ala.,

assignors to Monsanto Company, St. Louis, Mo., a corporation of DelawareFiled Sept. 21, 1964, Ser. No. 397,790 8 Claims. (Cl. 73-7) Thisinvention relates to a method and apparatus for testing wear resistanceof floor coverings and the like. More specifically this inventionrelates to a method which simulates actual stair tread wear on carpetsamples to produce data for predicting later stair tread wear of thecarpet when placed into use and apparatus for performing the method.

An analysis of carpet wear which occur on a stair tread reveals that thesection of carpet covering the front edge or nose of the stair treadreceives the heaviest wear. It has been demonstrated that thisaccelerated wear is primarily produced when the foot rolls over thefront edge of the carpeted stair step by persons ascending anddescending the stairs. The impact and abrasive forces imparted to thetufts at the tread nose by footwear crushes and flexes the tufts.Continued wear on the carpet causes an initial flattening of the tuftsfollowed by breaking and finally the actual attrition of fibers. Thus,the performance of a carpet is determined by the volume of traffic itcan withstand before the tufts are no longer distinguishable as such. Inorder that a more exact definition may be employed, thisindistinguishable condition will be referred to hereafter as the endpoint. By end point i meant the point during the test that one-half ofthe tufts along the line of heaviest wear are worn down to one-sixteenthof an inch.

Various attempts have been made to develop a laboratory test to simulatethe wear received by a carpet laid on stairs before an end point occurs.None of the known aparatus is considered to be satisfactory, however,since the test data cannot be correlated with actual stair tread weardata. The performance of the known apparatus is limited for the reasonthat data is affected adversely by the type finish on the carpet fibers,and the data does not represent signficant differences between differenttypes of carpet samples. Therefore, the end point cannot be predictedwith an acceptable degree of accuracy from test data compiled usingconventional carpet testing apparatus.

The currently accepted test for determining the wear resistance ofcarpets is by placing carpets on stairs which have a high volume oftraffic such as in a plant where most of the employees pass over thecarpet several times each day with each employee being counted andrecorded by a suitable counter. There are several apparent disadvantagesinherent in this method of testing carpets, the most objectionable beingthe time required for obtaining data, the number of samples which can betested is limited to the number of Stairways available, lack of controlover environmental conditions such as humidity and temperature, andvariability of carpet wear from the different steps. In view of theforegoing discussion, it would be highly desirable to have apparatuscapable of performing a simulated wear test on several carpet sampleswhich can be correlated with stair tread wear in the shortest timeperiod possible and yet predict wearability of carpets.

It is therefore an object of the present invention to provide a methodand apparatus for simulating actual stair tread wear on several carpetsamples simultaneously and ice in a uniform manner under controlledenvironmental conditions.

Another object of the present invention is to provide apparatus capableof imparting a simulated stair tread wear to several specimens of acarpet sample uniformly with respect to specimen positions.

Another object of the present invention is to provide apparatus capableof simulating the impact and sliding action which occurs between apersons shoe and carpet covering the front edge of stair steps.

Still another object of the present invention is to provide a method andapparatus to give carpets accelerated wear which represents significantdifferences between different types of carpet samples for obtaining testdata in a minimum time period.

A still further object of the present invention is to provide a methodand apparatus for obtaining from carpet samples simulated stair treadWear data which can be repeated on like samples.

Yet another object of the present invention is to provide a simulatedstair-wear test for carpets which reduces the specimen-to-specimen wearvariation of a given carpet sample.

A preferred embodiment for accomplishing the objects of the presentinvention contemplates a frame having a plurality of weighted armspivotally mounted to the frame with a shoe sole attached to one end ofeach arm and cam means for raising and lowering them in a manner whichcauses each shoe sole to strike a carpet sample fixed on a block. Theblock is mounted on a shorter pivotal radius than the shoe sole so thatthe carpet sample slips a short distance under the falling shoe sole asboth members rotate together in contact with each other therebysimulating the action of footwear rolling and slipping over the edge ofa stair step.

In accordance with the present invention, the discovery has been madethat the performance of carpets laid on stairs can be accuratelypredictd from test data recorded in a matter of hours rather than thetwo or more weeks normally required by the best known method consideredto be suitable for testing carpets fabricated from the natural andsynthetic fibers, and more particularly, the Acrilan and nylon fibers.

Other objects and advantages of the present invention will becomeapparent when the following detailed specification is read inconjunction with drawings in which:

FIGURE 1 is a perspective view of the invention illustrating apparatushaving six units;

FIGURE 2 is a side view of a single unit as seen from the cross-section2-2 of FIGURE 1; and

FIGURE 3 is a perspective view of a carpet sample removed from theapparatus shown in FIGURE 1 at the end of a test and illustrates the endpoint.

Referring now in detail to the drawing, there is shown in FIGURE 1 agroup of six units 10 mounted on a table-like frame 12 and connected toa power source 14 which operates all six units. As shown in FIGURE 2, aunit 10 is composed of a weighted member 16 and a block 18 positionedunderneath member 16 to cooperate with each other as will be describedhereafter. Member 16 is pivotally mounted to frame 12 by a pair of legs20 rotatably mounted on an axle 22 which is supported by a pair ofupright members 24 mounted on frame 12. A selected weight 17 which mustbe made to meet specific requirement is secured to member 16. On thebottom side of member 16, there is secured at the end opposite thepivotal connection a shoe sole 26 of the commercial type andintermediate the pivotal connection and the shoe sole a cam follower 28is positioned for cooperation with a cam to agitate movement of member16 as will be explained later.

The block 18 is pivotally mounted on frame 12 by a hinge 30 and issuspended at an angle elevated with respect to the frame by a tensionspring 32 connected between the block and a support arm 34 mounted onframe 12. The spring is held in a slightly elongated condition by a stopmeans 36 which limits the upward movement of block 18, but leaving theblock free to travel away from stop 36 when the tension of spring 32 isovercome. A sample specimen 40 of carpet is placed on the top side ofelevated block 18 facing toward member 16 and is held securely by aclamp 42. The carpeted block 13 is elevated so that an edge thereofsimilar to a stair tread nose is exposed to the striking force of member16. For better performance the sample specimen 40 is drawn tightlyacross the block and held in place to insure that wear is confined tothe tread nose area.

A rotatable shaft 44 is journaled in a plurality of bearing housingmounts 46 spaced longitudinally along frame 12 for supporting the shaft.The shaft is connected to power source 14 through a coupling 48 anddrive gear box 50. Positioned underneath each weighted member 16 is acam 52 secured to a shaft 44 for cooperation with cam follower 28 tooperate member 16 back and forth along an arcuate path upon rotation ofthe shaft. A variable speed changer 54 is associated with power source14 and gear box 50 for selecting a preferred r.p.m. rate for the shaftand a conventional counter 56 is mounted on the end of shaft 44 forrecording the total revolutions made by the shaft during a test period.A single counter has been found to be undesirable however when testspecimens from different types of carpet are being tested simultaneouslybecause of the delays caused by the different wear properties of thevarious samples. For these conditions, it is preferable to use anindividual counter for each unit 10.

In operation of the invention described above, a test specimen of carpet40 is clamped onto block 18 and the weighted member 16 is lowered towardthe test specimen until the cam follower 28 engages the cam 52. Thecounter 56 is set to Zero and the shaft 44 is driven by power source 14to raise and lower member 16. Rotation of the shaft 44 revolves thediscontinuous peripheral edge of cam 52 causing the shoe sole 26 tostrike the test specimen each time the cam moves through the positionshown in FIGURE 2. Further rotation of the cam in the direction denotedby the arrow cams the shoe sole out of contact with the test specimenand spring 32 retracts block 18 to its normal position against stop 36.The number of strikes per minute can be varied by adjusting speedchanger 54 to a preferred rate which is about 78 strikes per minute.This rate can be increased to approximately 100 however, beforeexceeding the recovery time of the carpet tufts between strikes.

The block on which the test sample is fixed moves downwardly under theweight imposed against the tension spring to produce a simulated actionof footwear rolling and slipping over the edge of a stair tread. Sinceone edge of the block is elevated toward the weighted member, the shoesole initially contacts the front edge of the covered block in a mannersimilar to a persons shoe on the edge of a carpeted stairstep. As theweight of member 16 elongates tension spring 32, the test specimen rollsdownwardly on a lesser radius than member 16 causing a scrubbing actionto occur between the test specimen and the shoe sole. In FIGURE 3 thereis shown a test specimen 70 which has been subjected to the simulatedtraflic. The worn area '72 illustrates the end point condition referredto earlier herein.

The following table represents data recorded from a carpet sample testedfor stair tread wear on a stairway having eighteen steps compared withdata recorded from .a simulated test in accordance with the invention oneighteen test specimens selected from the same carpet sample.

TABLE L-SPECLVIEN VARIATION (ACTUAL vs. SIMULATED) Step and/or Trafficat End Point Tratfic at End Point Specimen Number (Steps) (thousands)(Simulated) (thousands) 22. 2 5. 6 .1 18. 8 5. 6 31 18. 8 5. 6 4. l8. 8o. 1 5 28. 0 4. 4 6. 18.8 6 8 7 20. 8 5. 5 8 27. 2 5. 8 9 21. 8 5. 9 10"21. 8 5. 4 11.. 28. 8 5. 5 12.. 28. 8 5. 8 131. 28. 5 6. 6 14.. 36. 5 6.6 l5 .i 45.0 7.0 l6 o, 45.0 7. l 17 42. 8 6. 4 18 c. 45. O 6. 6

Average 28. 7 6.0 Range 26.2 2. 7

The data shown in Table I illustrates clearly that significantdifferences in wear occurs between different steps on the stairway. Someof the variance can be attributed to such conditions as the amount andtype of abrasive particles tracked onto the carpet, the weight of theperson using the stairway, the type shoe soles worn, and the weight ofthe persons. All of these factors tend to lower the confidence rate atwhich carpet performance can be predicted. It will be noted from thedata above however, that a comparative test conducted in accordance withthe invention reduces the amount of variation from specimento-specimen.Thus, the data compiled with the apparatus shown in FIGURE 1 provides areliable basis for making an accurate prediction on carpet performance.

Carpet samples from eight carpets of a different type were subjected tosimulated traffic and stair traffic until the wear reached end point.The results appear in Table II.

TABLE II Simulated Traflic Stair Traffic Sample No. at End Point EndPoint (thousands) (thousands) The data illustrates the correlation ofthe wear charac teristics of different samples of carpet when tested bythe two methods shown. Although the simulated wear reaches the end pointwith substantially less traffic, the difference between the differentsamples may be correlated with the corresponding stairway data.

From the foregoing description and data it will be apparent thatwearability produced by the apparatus in accordance with the proceduresdisclosed herein is uniform and reliable for accurately predictingfuture performance of carpets and other floor coverings. Moreover, theinvention provides vmeans for testing several samples under controlledenvironmental conditions in a minimum time period.

Although the invention has been described as apparatus for testing wearresistance properties of carpets, it is to be understood that theinvention is applicable to all types of floor coverings and may beadapted for testing the physical properties of other materials withoutdeparting from the inventive concept disclosed herein.

We claim:

1. Apparatus for testing wear resistance properties of a test specimencomprising, in combination, a table-like frame, a member having anabrasive surface at one end portion, said member being mounted to theframe and pivoted at the opposite end for movement of said abrasivesurface along an arcuate path, a block covered with a test specimen andpivotally mounted to the frame, stop means associated with said blockfor limiting upward movement of said block away from said frame, atension spring connected to the block for maintaining the block againstsaid stop means to elevate the test specimen with respect to said frame,and means for agitating said abrasive surface along said arcuate pathinto contact with said test specimen and extending the tension springwhereby the test specimen is pivoted on a lesser radius than theabrasive surface to produce a sliding action between the abrasivesurface and test specimen.

2. Apparatus for testing wear resistance properties of a carpet samplecomprising, in combination, a table-like frame, a rectangular memberpivotally mounted to the frame, said rectangular member having a shoesole and cam follower mounted to the bottom side thereof with respect tothe frame, a carpet covered block pivotally mounted to the frame, asupport arm extending from the frame, a tension spring connected to saidblock and said arm, stop means for maintaining said block in an elevatedposition, a shaft mounted for rotation on the frame, a cam fixed to theshaft for rotation therewith, said cam being positioned to cooperatewith the cam follower to agitate the shoe sole along an arcuate pathwherein contact occurs intermittently between the shoe sole and thecarpet covered block, and means for driving the shaft at variablespeeds.

3. The apparatus of claim 2 further characterized by a plurality ofpositions for simultaneously testing a plurality of carpet samplesindependent of each other.

4. Apparatus for testing wear resistance properties of a test specimencomprising, in combination, a frame, a load member having an abrasivesurface pivotally mounted on said frame for travel along a first arcuatepath, a test specimen pivotally mounted or travel along a second arcuatepath of substantially lesser radius than said first arcuate path, meansfor restraining said test specimen in an elevate-d position with respectto the frame against a stop limiting means, means for oscillating theload member back and forth along the first arcuate path to contact aportion of the test specimen causing the test specimen to travel alongthe second arcuate path in contact with the abrasive surface whereby asliding and rolling action occurs between said specimen and saidabrasive surface.

5. The apparatus of claim 4 wherein the abrasive surface is aconventional shoe sole.

6. The apparatus of claim 4 wherein means are provided for testingsimultaneously a plurality of samples independently of each other.

7. A method for testing the wear resistance properties of a test samplecomprising directing a pivoted member having an abrasive surface spacedfrom the pivotal point along a first arcuate path, positioning a testsample suspended on a pivot in the arcuate path of the abrasive surface,agitating the abrasive surface in a clockwise direction about itspivotal point into contact with the test sample causing said sample torotate counter clockwise about its pivotal point along an arcuate pathhaving a substantially smaller radius than said first arcuate paththereby producing a lateral sliding action between the abrasive surfaceand test sample, and returning the abrasive surface and test specimen totheir normal position.

8. The method of claim 7 wherein a plurality of carpet samples aretested simultaneously and independent of each other.

References Cited UNITED STATES PATENTS 974,450 11/1910 Tully 73-7 X2,942,463 6/1960 Mann et al 737 X 3,121,320 2/1964 Bauer 73-7 3,134,2555/1964 Oliver et al 737 DAVID SCHONBERG, Primary Examiner.

1. APPARATUS FOR TESTING WEAR RESISTANCE PROPERTIES OF A TEST SPECIMENCOMPRISING, IN COMBINATION, A TABLE-LIKE FRAME, A MEMBER HAVING ANABRASIVE SURFACE AT ONE END PORTION, SAID MEMBER BEING MOUNTED TO THEFRAME AND PIVOTED AT THE OPPOSITE END FOR MOVEMENT OF SAID ABRASIVESURFACE ALONG AN ARCUATE PATH, A BLOCK COVERED WITH A TEST SPECIMEN ANDPIVOTALLY MOUNTED TO THE FRAME, STOP MEANS ASSOCIATED WITH SAID BLOCKFOR LIMITING UPWARD MOVEMENT OF SAID BLOCK AWAY FROM SAID FRAME, ATENSION SPRING CONNECTED TO THE BLOCK FOR MAINTAINING THE BLOCK AGAINSTSAID STOP MEANS TO ELEVATE THE TEST SPECIMEN WITH RESPECT TO SAID FRAME,AND MEANS FOR AGITATING SAID ABRASIVE SURFACE ALONG SAID ARCUATE PATHINTO CONTACT WITH SAID TEST SPECIMEN AND EXTENDING THE TENSION SPRINGWHEREBY THE TEST SPECIMEN IS PIVOTED ON A LESSER RADIUS THAN THEABRASIVE SURFACE TO PRODUCE A SLIDING ACTION BETWEEN THE ABRASIVESURFACE AND TEST SPECIMEN.